This invention relates to a retainer for a roller bearing used in automotive transmissions and other ordinary machinery, and more specifically relates to a structure for retaining rollers in the pockets formed in the retainer.
A retainer for a roller bearing is required to positively prevent dropouts of needle rollers, to be easy to handle and easy to assemble rollers.
There are two known methods for retaining rollers in such a retainer. One method, shown in FIGS. 11 and 12, comprises the steps of punching a steel strip 21 using a punch and a die to form pockets 22 for retaining rollers, and forming upper and lower stopper lugs 23 and 24 by caulking both sides of the pockets 22 with jigs 26 and 27 to prevent rollers 25 from dropping out of the pockets. After forming the stopper lugs, the steel strip 21 is rolled into an annular retainer.
In the second method, shown in FIGS. 13 and 14, crossbars 32 defining roller pockets 31 are bent so that they are partially located below the central axis of each roller and partially above it. As shown in FIG. 14, the upper and lower portions of the crossbars 32 serve as upper and lower stopper lugs for preventing the rollers 33 from dropping out of the pockets.
In the first method, side surfaces of the pockets 22 formed by punching comprise a flat shear surface a formed on the punching starting side and an outwardly deflected broken surface b formed on the side remote from the punching starting side. If the side surfaces are caulked by lug-forming jigs 26, 27 from the shear surface a toward the broken surface b, dimensional variations of the lugs tend to increase. Such lugs may be too small in the amount of projection or in an extreme case, lugs may not be formed at all.
In the second method, since the rollers 33 are held in position making use of the thickness of the crossbar portions 32, their thickness has to be less than 1/2 of the roller diameter. But if the roller diameter is small and the inner diameter of the retainer is relatively large, the thickness-to-diameter ratio of the retainer may decrease to such an extent that its rigidity is insufficient.
U.S. Pat. No. 3,494,684 discloses a retainer for a roller bearing in which the side faces of the pockets are partially ironed to form roller stopper lugs at the diametrically outer and inner ends of each pocket. In this case, the entire side faces of the crossbars not subjected to ironing are used as guide surfaces for the rollers.
One problem of this arrangement is that it is difficult to form guide surfaces uniformly and with high accuracy because large part of the side faces of crossbars is used as roller guide surfaces.
Moreover, burrs will be inevitably formed by ironing. If such burrs are left unremoved, they will interfere with rollers, making it difficult to smoothly guide the rollers.
An object of this invention is to provide a retainer for roller bearing which has a high strength and is high in mass-productivity, and a method of manufacturing the same which makes it possible to form roller stopper lugs and roller guide surfaces reliably without being influenced by broken surfaces formed by punching or by burrs formed by ironing.